The present invention relates to locating a welding seam for purposes of centering ultrasonic test equipment which non-destructively examines e.g. a submerged arc welded seam of pipes.
Ultrasonic test equipment is, for example, particularly positioned in a test stand, and the test object such as a pipe is passed past the equipment. Proper testing requires that the equipment and here particularly the individual ultrasonic test heads and transducers have a well defined position in relation to the seam. Moreover, that position should be related to the center line of the seam.
Locating the welding seam can be carried out for example inductively by using the geometric irregularities in the material next to the welding seam. Moreover, the seam itself must have a particular height above the surface contour of the parts being welded (e.g. the cylinder as defined by the outer surface vs. a pipe). Such a elevation must exceed 1 millimeter. For lower heights or elevations, the weld center may escape detection. Also, inductive measurement is rather temperature sensitive so that additional errors must be expected on that account.